Method for producing a thermoplastic synthetic yarn having a latent crimp

ABSTRACT

A drawing method and device for thermoplastic synthetic yarn is disclosed, by which simultaneously a latent crimp is imparted to the yarn, wherein the yarn is drawn by means of a heated drawing roll, the contact between the yarn and the heated surface of the roll is not continuous. The invention contemplates also the yarn thus obtained and the textile articles made by the yarns as above referred.

United States Patent 1151 3,673,650

Cerutti 1 1 July 4, 1972 54 METHOD FOR PRODUCING A 2,975,474 3/1961 Smith ..264/l67 THERMOPLASTIC SYNTHETIC YARN 2.21 3123 :32? Qdams ascy HAVING A LATENT CRIMP 3,425,206 2/ I969 Holton [72] Inventor: Giacomo Cerutti, Gozzano, ltaly 3,444,682 5/1969 Polacco et al.

3,491,418 l/1970 NicotaetaL {73] Assgnee 3,421,193 l/1969 Taylor [22] Filed: April 29, 1970 3,422,491 1/1969 Kihara et al.

3,479,710 11/1969 Turton et al... [21] APPL l6,2t5 12/1856 Reynolds 2,930,103 3/1960 Stanley ..28/7l.3 [30] Foreign Application Priority Data I Primary Examiner-Jay H. Woo Mdy l9, A"0',ney Di"er Brown & [52] U.S.Cl. ..28/72.1, 18/] FT, 28/713,

28/72.]5, 264/168, 264/290 [57] ABSTRACT v [51] Int. Cl. ..B29c 17/02, DOld 5/22 A drawing method and device for thermoplastic synthetic yarn [58] Field of Search ..264/290,167,l68;28/1, 1.8, is disclosed, by which simultaneously a latent crimp is im- 28/72.1, 72.15, 71.3; 18/] FT parted to the yarn, wherein the yarn is drawn by means of a heated drawing roll, the contact between the yarn and th [56] References Cited heated surface of the roll is not continuous. 1

UNITED STATES PATENTS The invention contemplates also the yarn thus obtained and the textile articles made by the yarns as above referred. 2,778,058 1/1957 Gabler ..264/210 Z 2,917,779 12/1959 Kurzke et al. ..264/290 '1" 4 Claims, 1 Drawing Figure METHOD FOR PRODUCING A THERMOPLASTIC SYNTHETIC YARN HAVING A LATENT CRIMP The present invention relates to a method for drawing thermoplastic synthetic yarns and imparting to them simultaneously a latent crimp, in which method the drawing is made by means of two cooperating feeding rolls, rotating at a predetermined peripheral speed, and a heated draw toll, rotating at a peripheral speed greater than the feeding rolls and on which the yarn makes several complete windings.

It is generally known to draw thermoplastic synthetic yarns, as for instance polyarnide and polyestere yarns, using a heated draw roll. The contact surface of the draw roll with the yarn, i.e. the surface corresponding to the exterior circumference of the draw roll, on which the yarn usually makes several windings, is normally a smooth surface or at the most lightly rough surface, but such to assure practically a continuous contact of the yarn or in any case a uniform heating of all the yarn length that winds on the draw roll.

As a result of drawing with a heated draw roll, the thermoplastic synthetic yarns, to which relates the present invention, show a reduced shrinkage, when are subjected to determined treatments, for instance after immersion in boiling water. These yarns do not show however any tendency to crimping after the treatment in boiling water; that means then, they don't show latent crimp. It has been new found that it is possible. to impart to the synthetic thennoplastic yarns a latent crimp while they are drawn with a heated draw roll if the contact of the yarn on the draw roll surface is not continuous in such a way that during the residence of the yarn on the draw roll, portions of continuous contact between yarn and heating surface, having a length from 1 to mm., are altemated by portions with no contact between yarn and heating surface, having a length from 1 to 15 mm.

It has been noticed that in some contact portions with length lower than 1 mm, the crimp effect is very little perceptible; on the contrary if the contact portions have a length higher than 15 mm, the crimp appears quite feeble.

It is not necessary, as the invention aims, that the portions having continuous contact and the portions having no contact with the hot surface, have the same length.

The method of the present invention can be realized by drawing the thermoplastic synthetic yarns with a heated draw roll, whose profile is toothed.

The aims of the present invention are advantageously reached if the profile of each tooth head is formed by an arch of the exterior circumference on the toothed draw roll having a length between 1 and 15 mm, each tooth being separated from the adjacent teeth by a distance between 1-15 mm, measured as arch of the exterior circumference of the toothed draw roll.

Generally it will be preferred to realize the draw roll toothing in a symmetrical manner, such that the length of each tooth head is equivalent to the distance between each tooth and the adjacent teeth. Anyway it is possible to realize the draw roll toothing in a symmetrical manner.

The toothed draw roll, as to the present invention, can be heated with any known means: electrically, with a heating fluid, by the radio-frequency field and so on. I

The temperature of the draw roll contact surface is conveniently included between 100 C and 200 C, according to the nature of the thermoplastic synthetic yarn subjected to the drawing. The empty space between one tooth and the other can be, if wished, filled of heat insulating material, in order to make clearer the difference between the yarn portions having continuous contact with the surface of the teeth head of the drawing roll and the yarn portions not in contact with the heating surface. For a better explanation of the invention, we shall now relate to the enclosed drawing, showing schematically a drawing position on a known type of drawtwisting machine.

The yarn l is unwound from the spinning bobbin 2, through the eyelet thread guide 3, by the two feeding rolls 4 and 5, of which 4 is the roll moved positively and 5 is the counter-roll.

The grooved thread guide 6 divides the winding turns of the yarn on the counter roll 5. The toothed draw r0 1 7 draws the yarn l in the space included between thefeeding rolls 4 and 5 and the draw roll 7. Thedraw roll 7 is heated. The yarn 1, coming from the feeding rolls, winds several times on the draw roll 7, then passing the idler roll 8 goes towards the winding system formed by a twisting spindle, provided with the ring 9, on which is steadily fixed the tube 10, on which is fonned the yarn package I]; the eyelet thread guide 12 restricts to the top the twisting balloon fonnation.

The invention will be further explained by the following example.

EXAMPLE A polycaprolactam yarn of 20 filaments was drawn on a known drawtwisting machine, having as draw roll, a toothed draw roll, electrically heated. The exterior circumference of the toothed draw roll had a diameter of mm, the teeth number was 38, the distance between the adjacent teeth was 5 mm, for which the length of each tooth head profile was about 5 mm.

The yarn was drawn at a speed of 250 m/min and the draw ratio was calculated in such a way to have a final count of 78 dtex and an elongation at break of 35 percent. The toothed roll surface was heated at C. A skein of the yarn so produced was kept in boiling water for 5 minutes. When it dried a remarkable crimp was noticed in the yarn. Another skein of the same yarn was exposed to the saturated steam at the pressure of 1 atm. for 5 minutes. At the end of this treatment, the yarn showed a crimp comparable to the previous one.

What is claimed is:

l. A method of drawing a thermoplastic yarn of the class including polyarnide and polyester yarns and simultaneously imparting thereto a latent crimp, said method comprising the steps of positively feeding the yarn at a first rate at a first point and positively feeding the yarn at a spaced second point at a second and greater rate to draw the yarn between said first and second points, and at said second point simultaneously with the drawing of the yarn heating short lengths of the yarn at spaced intervals utilizing solely a heated toothed draw roll about which the yarn passes at least substantially one complete turn to provide firm anchorage of said yarn relative 'to said draw roll for effecting the drawing and heating of said yarn.

2. The method of claim 1 wherein the surfaces of said draw roll are heated to a temperature ranging between 100 C. and 200' C.

3. The method of claim 1 wherein the length of each heating of said yarn is between 1 mm and 15 mm and the spacing between adjacent heatings of said yarn being between 1 mm and 15 mm. 

1. A method of drawing a thermoplastic yarn of the class including polyamide and polyester yarns and simultaneously imparting thereto a latent crimp, said method comprising the steps of positively feeding the yarn at a first rate at a first point and positively feeding the yarn at a spaced second point at a second and greater rate to draw the yarn between said first and second points, and at said second point simultaneously with the drawing of the yarn heating short lengths of the yarn at spaced intervals utilizing solely a heated toothed draw roll about which the yarn passes at least substantially one complete turn to provide firm anchorage of said yarn relative to said draw roll for effecting the drawing and heating of said yarn.
 2. The method of claim 1 wherein the surfaces of said Draw roll are heated to a temperature ranging between 100* C. and 200* C.
 3. The method of claim 1 wherein the length of each heating of said yarn is between 1 mm and 15 mm and the spacing between adjacent heatings of said yarn being between 1 mm and 15 mm.
 4. The method of claim 1 wherein the yarn is passed around the draw roll at least several times. 